1. Field of the Invention
The present invention relates to poly(carbonate-siloxane) resin compositions and more particularly relates to poly(carbonate-siloxane) resin compositions having reduced tendencies to burn.
2. Description of Related Art
Poly(carbonate-siloxane) copolymers are known elastomeric materials and blends of poly(carbonate-siloxane) copolymers with thermoplastic resins such as polyesters and polycarbonates are known (See, for example, Avakian, U.S. Pat. No. 4,616,042). While the aforementioned poly(carbonate-siloxane) copolymers and blends have useful properties such as high yield elongations, these copolymers and blends typically exhibit flame test burning levels which are above those desired for particular electrical and aerospace applications.
While polycarbonate compositions have been rendered flame resistant by the incorporation of an aromatic sulfone sulfonate, (See, for example, Mark, U.S. Pat. No. 4,092,291) these compositions have lacked the desired level of elasticity and/or flexibility necessary for many electrical wiring applications such as wire and cable insulation. Polycarbonate-siloxanes, on the other hand, while possessing the required level of elasticity, have a tendency to degrade at elevated temperatures in the presence of alkalis such as the aforementioned sulfone-sulfonate and one would expect reduced molecular weight materials to exhibit an increased tendency to burn.
Accordingly, one obJect of the present invention is to provide poly(carbonate-siloxane) resin compositions having reduced tendencies to burn and exhibiting high levels of elasticity.